1. Field of the Invention
This invention relates to a wrenching tool, and in particular to a hand tool useful for application of torque limited fasteners in minimum distance applications.
2. Brief Statement of the Prior Art
Torque limited fasteners, known as frangible fasteners are used extensively in the aerospace industry. These fasteners employ a threaded nut member which has a threaded locking collar and a distal wrenching ring joined to the locking collar by a neck with a notched section which shears from the collar when the applied torque exceeds a predetermined value. Often the threaded collar has an upset portion, usually a slightly elliptical shape to provide a frictional spring lock that prevents the fastener from spinning off in the event that the residual tension on the fastener is lost.
These fasteners are usually applied with power driven, or hand, wrenching tools having sockets which engage the distal wrenching ring to apply the threaded collar and twist the wrenching ring from the threaded collar when the predetermined torsional loading is exceeded.
It is frequently necessary to apply the torque limiting fasteners in very tight quarters, where a power driver cannot be used. It also becomes necessary to install the fasteners very close to a raised obstruction such as a splice plate, which may have been added to the airframe after initial manufacture. In these minimum edge distance installations, there is insufficient clearance to apply the sockets of conventional wrenches over the wrenching collar of the fastener.
Heretofore, no entirely suitable tool has been devised for these installations. While various hand tools such as pliers and vise grip clamps could be used, they are difficult to use, and their application is not approved, since if they were applied to grip the locking collar directly, the torque limited design of the fasteners would be defeated.